1. Field of the Invention
This invention relates generally to low pass filters and more particularly to a low pass filter employing analog to digital conversion and digital averaging techniques.
2. Description of the Prior Art
Low pass filters for recovering low frequency components of a signal spectrum are well known in the art. Analog techniques utilizing linear R-C networks are often employed to filter an analog signal. However, R-C networks do not lend themselves to practical implementation with complex IC technology. Additionally, the stability of linear filters is a function of the resistor and capacitor component parameters, which may vary with age and temperature and which vary from one component to another, thereby requiring alignment in the factory. Also, linear R-C type filters are not ideal filters in that the signal passed by such a filter includes small contributions from signals received in the past.
Digital filtering techniques have also been used in the past, but these techniques often require high speed multipliers, shift registers, read-only memories (ROM's), and a plurality of adders. These prior art digital filters require large amounts of chip area when fabricated as an integrated circuit, thereby reducing wafer yields and resulting in higher cost. Thus, it will be appreciated by those skilled in the art that a low pass digital averaging filter which can easily be implemented within an integrated circuit and which requires a small amount of chip area is a significant improvement over the prior art.